Security guard David Dunn uses his supernatural abilities to track Kevin Wendell Crumb, a disturbed man who has twenty-four personalities.
After pursuing Kevin Wendell Crumb and the multiple identities that reside within. David Dunn finds himself locked in a mental hospital alongside his archenemy, Elijah Price and must contend with a psychiatrist who is out to prove the trio do not actually possess superhuman abilities
Following the conclusion of "Split", "Glass" finds David Dunn (Bruce Willis) pursuing Kevin Wendell Crumb's (James McAvoy) superhuman figure of The Beast in a series of escalating encounters, while the shadowy presence of Elijah Price (Samuel L. Jackson) emerges as an orchestrator who holds secrets critical to both men.
- Nearly 20 years after turning in Elijah Price to the authorities at the ending of "unbreakable" (2000), David Dunn has embraced his superhuman vigilante ego dubbed "The Overseer" and is aided by his now adult son Joseph. After apprehending two male delinquents who have assaulted a man for views on the internet, Dunn returns to his business of "Dunn Home Security" and it is revealed that he is hunting after Kevin Wendell crumb/Horde/Beast, after the events of his exploits in the events of "Split" (2016) which in this time-line occurred 3 weeks ago. Upon returning home, David struggles with the fact that his wife left him, not being able to cope with her husbands superhuman exploits and beliefs.
Meanwhile, Kevin Wendell Crumb/The Horde has kidnapped a small group of cheerleaders and holds them hostage, preparing to feed them to the Beast in an abandoned factory. Dunn walks through the streets the next morning, brushing against people who pass him by in the crowds in order to see into their past and deduce who the Beast is. He brushes against the nine-year-old personality of Kevin and sees a flashback of him speaking to corpses of young women his ego the Beast had just killed. That night, while Kevin transforms into the Beast and presumably attacks a group of homeless people, Dunn dons the rain-slicker overcoat of the Overseer and arrives at the factory. After freeing the girls, he is attacked by the Beast who is quicker and more agile than him. But Overseer is stronger than the Beast, and when the Beast attempts to crush him, Overseer leaps out of a nearby window, causing them both to land in the streets below.
The two rise up and charge each other once more but are stopped by a group of police led by a mysterious woman who encourages Dunn to give himself up to avoid hurting officers of the law. The Beast is conditioned by flashing lights which the force have and is reduced to a confused and scared Kevin. The two are then arrested and brought to Raven Hill Memorial Institution. Joseph watches helplessly as his father and Kevin are placed in holding cells. Dunn is placed in a room with water sprinklers which will go off if he attempts to escape. Kevin is held in a room with hypnosis lights meant to flash should he ever show outright forms of violence. Also in the Institution is Elijah Price, still serving his time for bombing the Eastrail 177 in order to find David Dunn and discover his powers of physical invincibility. The mysterious woman from earlier reveals herself to be Dr. Elle Staple, a psychiatrist.
Elle Staple tries to convince the men that they are normal people with compulsions of grandeur but consistently fails. She then tries to appeal to Price's mother, Joseph Dunn, and Casey Cooke, former victim and friend of Kevin, but fails again. Staple gives the men three days to be convinced that they are deluded figures and not super-humans, otherwise they will be handed over to trial for their crimes. Staple then calls Dunn and Kevin into a room to test their psyches. However, a seemingly dormant and unresponsive Elijah Price (still wheelchair-bound from the broken spine he received from his fall down a flight of stairs in "Unbreakable") is wheeled in and brought alongside the men, much to David Dunn's disgust in being associated with him. During the meeting, Staple brings to mind Kevin's past abuse from his mother which spurred the transformation of the Horde, as well as the time David was nearly drowned in a swimming pool which nearly killed him- bringing to mind the first time water was revealed to be his kryptonite. She then tests Price's psyche by bringing to mind a time in which he broke his arm on a ride at a carnival, bringing to mind the extreme fragility of his bones.
Later that night, Elijah Price breaks free from his cell and meets with Kevin who is in his "Patricia" personality. After an intelligent discussion, Elijah Price reveals that he has not been taking his sedative medication and instead hiding it inside his wheelchair, thus keeping his wits about him and sharp as ever. He encourages Kevin/Patricia to meet with him the next night and show him the "Beast." Before Price leaves Kevin/Patricia asks what his name is. Price turns his head and replies, "First name Mister....Last name...Glass."
Upon returning to his room, Price is captured by Staple who performs a pre-frontal lobotomy on him knowing that his genius must be quelled before he can put any plan into motion. The seemingly brain-dead Price is brought back to his cell but suddenly comes alive and kills his caretaker by slashing his throat with a shard of broken glass. It is then revealed that Price had planned to be caught by Staple, and had sabotaged the machine earlier should the operation be conducted on him. Price then escapes to Kevin's cell and deactivates the "hypnotic lights." He and the beast make their way to a secret room where Kevin transforms into the Beast and looks over Price, discovering that he has been broken. The Beast immediately takes a liking to Price but not before Price explains his plan to have the Beast and the Overseer battle each other at the top of the highest skyscraper in the city of Philadelphia which has just been erected. It is there that the whole world will see and discover that superheroes do indeed exist. The Beast agrees and helps Price make his way through the facility.
Price then communicates with David in his cell and explains that he had deactivated the water sprinklers. He encourages David to escape but David initially refuses. Price then explains that should David refuse to escape and fight the Beast, Price will blow up a chemical company, killing many people. Having no other, choice, David reluctantly breaks down the door and dons his rain slicker and runs out of the institution.
Price and Beast begin by confronting an orderly who had maltreated Price for years earlier. The Beast crushes the orderly and forces him to kneel before Price before beating him to death as Price watches, shaking his head at the man's stubbornness. The Beast then wheels Price through the halls, beating down every security force that tries to hinder them. The Beast then captures two nurses and forces them into a van where he keeps them hostage. Two police officers show up but the Beast makes short work of them.
Price's mother, Joseph, and Casey arrive in time to see the Beast see the Overseer approaching. Price sits back in his wheelchair and watches in excitement as the Beast charges Overseer and the two engage in a fight. Staple also sees this and calls up security. Casey rushes out, hoping to calm Kevin down but he is too busy fighting Overseer. Price recognizes her as "the one the Beast let go" and smiles in fascination at her. Armed policemen arrive and separate Overseer from the Beast, by are quickly overpowered by each of them. Overseer manages to push the forces attacking him into an enclosed compartment before locking them in while the Beast manages to kill and eat some of his attackers. Overseer frees the nurses the Beast had held hostage and is then attacked by the Beast who has been informed by Price that the Overseers weakness is water, as well as directing him to a water tank the institution uses.
Joseph intervenes and explains to Kevin that Kevin's father was on the Eastrail 177 as well which Price had destroyed, thus killing Kevin's father and creating the Beast. Upon hearing this, Price is overcome with delight and amazement upon realizing he created both a superhero and a super-villain, and declares himself a mastermind. The Beast thanks Price for creating him, but then explains that he must protect Kevin at all costs- right before breaking Price's collarbone. Overseer tries to distract Beast, saying that his fight is with him, which Price finds amusing. The Beast then punches Price in the chest, breaking his ribs which pierce his lungs and mortally wound him. Price exclaims with pain and falls out of his wheelchair, dying upon the ground.
The Beast flings Overseer/David Dunn into the water tank and fights him in there, easily overpowering him. But Dunn manages to break through the wall and the two splash out onto the institution's lawn. The water from the tank pours out as well and fills a nearby pothole. The Beast says to Dunn that they will finish their battle at the top of the skyscraper and begins running off in that direction. Staple convinces Casey to calm the Beast down to avoid any other violence and she agrees. Casey catches up to the Beast and appeals to him, causing him to calm down and revert back to the innocent Kevin. Once his defenses are down, a sniper shoots Kevin in the stomach now that the bulletproof skin of the Beast is gone. Kevin bleeds out and begins dying.
More police forces show up and Joseph asks them to help his father as he is very weak. One of the Security forces grabs David and drags him over to the water-filled pothole, forcibly drowning his face in it. David is too weak to fight back and his easily overcome. Staple arrives and orders the guard to wait as she grabs David's hand. He then sees a flashback to her life in which she is a member of a secret society who monitors the actions and works of superhuman beings and quells them should they draw too much attention. She asks David that if she convinced him he was human she would have let him live, but Price's and the Beast's machinations prevented that. She then leaves and David realizes his true insignificance as the guard repeatedly bashes David's face into the puddle, ruthlessly drowning him.
Kevin dies in Casey's arms, finally finding the light and finding peace in the safety of his friend's arms. Elijah lays dying in the parking lot, a broken and pitiful mess. Staple arrives and tells him that she and members of her following have suppressed superhuman masterminds to retain a safe society to prevent overarching divides of "gods" among men. After Staple leaves, Elijah Price's mother kneels over her dying son. Price explains painfully that he was not a mistake to which his mother smiles proudly at him saying, "No. You were spectacular." Price smiles wryly and dies peacefully.
Believing her mission a success, Staple deletes the footage of all the security cameras which recorded the fight between Overseer and Beast. However, upon closer examination she realizes that Price had hacked the computers and live streamed all the events to a private network. Thus, it was never Price's plan to escape the facility and force the Beast to battle Overseer at the top of the skyscraper, as such a plan would be too elaborate. His plan and everything he had worked for was now a complete success. Staple leaves the security room and screams in anger realizing her failure. Price's mother, Joseph, and Casey receive copies of the footage and upload it, revealing it all to the public in the Philadelphia skyscraper. The film ends with them sitting together as the videos of Overseer and the Beast and their fantastic feats are relayed and spread to everyone's feed and to the daily news, revealing the world of superheroes to the public.
The main title of "Glass" appears on the screen one last time and the end credits are laced with shards of glass through which scenes from the film as well as the previous films of "Unbreakable" and "Split" connecting the whole story together.